1. Technical Field
The present disclosure relates to an apparatus for detecting a fault in a power relay of an inverter.
2. Description of the Related Art
When an inverter is started, initial charging is carried out. During the initial charging, a power relay connected in parallel to an initial charge resistor is opened. The initial charge resistor serves to prevent an inrush current during the initial charging. Thereafter, the power relay of the inverter is closed using a control signal for normal operation of the inverter.
FIG. 1 is a diagram illustrating a current flow during the initial charging of the inverter.
Referring to FIG. 1, a converter stage 20 converts alternating current (AC) into direct current (DC) and provides a smoothing circuit with the direct current (DC).
The smoothing unit typically includes a DC link in which a capacitor 13 is disposed, a resistor 11, and a power relay 12.
When the inverter is driven, a current flows as indicated by arrow {circle around (1)} of FIG. 1. This is to prevent an inrush current during introduction of the initial current. When the power relay 12 is closed (ON) by a control signal generated inside the inverter, a current flows as indicated by arrow {circle around (2)}. The current flows as indicated by arrow {circle around (2)} even when a motor 40 is driven, and an output current to an inverter stage 30 increases, such that the current (idc) also increases. If the power relay 12 is damaged during driving of the motor 40, the current may flow again as indicated by arrow {circle around (1)}, such that the current flowing in the initial charge resistor 11 may deviates from rated capacity. As a result, the initial charge resistor 11 may be damaged and may causes heat, such that the internal structure of the inverter may also be damaged.